Provisional tibial prosthesis system

ABSTRACT

The present disclosure provides a provisional tibial prosthesis system for a set of prosthetic knee joints for implantation in a natural knee, the provisional tibial prosthesis system including a bearing component and a bearing support, the spacing of the bearing component from the bearing support is adjustable to allow for representation of a variety of different sized final tibial prostheses. In this system, only one provisional bearing component corresponding to each level of constraint is needed and shims are used to adjust the spacing of the bearing component from the bearing support. The shims are slidably insertable between the bearing component and the bearing support in an anterior/posterior direction to allow for adjustment of the spacing of the bearing component from the bearing support. The number of provisional components needed during knee surgery is reduced and adjustment of the system only requires the knee join to be distracted by a distance equal to the height of a particular shim.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/424,222, filed Dec. 17, 2010, the entire disclosure of whichis hereby expressly incorporated by reference herein.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates generally to provisional orthopediccomponents used to replicate final orthopedic components during asurgical procedure. More particularly, the present disclosure relates toprovisional tibial components that assist in determining the proper sizeof a final tibial prosthesis for a prosthetic knee joint for replacementof all or part of a natural knee.

2. Description of the Related Art

Knee replacement provisional components are positioned on a distal femurand/or a proximal tibia to allow range of motion testing so that asurgeon can verify proper sizing of final prosthetic components. Kneereplacement systems may include a wide variety of tibial bearingcomponents, including bearing components which cooperate to form aposterior stabilized prosthesis, a cruciate retaining knee prosthesis ora knee prosthesis having an intermediate level of constraint between aposterior stabilized and cruciate retaining prosthesis. Such systemsinclude a high number of provisional components corresponding to thediffering constraint levels offered by the system as well as thedifferent sized bearings for each constraint level. During knee surgery,a surgeon may remove and replace a provisional tibial bearing componentof a first size with a provisional tibial bearing component of a secondsize to adjust the ligament tension of the knee joint. Efforts have beenmade to lessen the number of provisional components needed during kneesurgery, including the use of adjustable tibial components having anadjustable height to allow the adjustable tibial component to mimic avariety of different sized final tibial prostheses.

One such device includes a spacer block positioned between a provisionalbearing component and a tibial tray to provide additional spacing of theprovisional bearing from the tibial tray. However, these devices requiredistraction of the knee joint to secure the spacer block to the bearingcomponent and the tibia tray.

SUMMARY

The present disclosure provides a provisional tibial prosthesis systemfor a set of prosthetic knee joints for implantation in a natural knee,the provisional tibial prosthesis system including a bearing componentand a hearing support, the spacing of the hearing component from thebearing support is adjustable to allow for representation of a varietyof different sized final tibial prostheses. In a provisional tibialprosthesis system, there is, among other things, a bearing surface thatarticulates with a femoral prosthesis component. Knee replacementsystems may include a wide variety of bearing components, includingbearing components which cooperate to form a posterior stabilizedprosthesis, a cruciate retaining knee prosthesis or a knee prosthesishaving an intermediate level of constraint between a posteriorstabilized and cruciate retaining prosthesis. In the system of thepresent disclosure, instead of a system that includes a high number ofprovisional components corresponding to the differing constraint levelsoffered by the system as well as the different sized bearings for eachconstraint level, only one provisional bearing component correspondingto each level of constraint is needed and shims are used to adjust thespacing of the bearing component from the bearing support.Advantageously, the number of provisional components needed during kneesurgery is reduced and adjustment of the system only requires the kneejoint to be distracted by a distance equal to the height of a particularshim.

In one embodiment, the present disclosure includes a plurality of shimsslidably insertable between a bearing component and a bearing support inan anterior/posterior direction to allow for adjustment of the spacingof the bearing component from the bearing support. Advantageously, thepresent disclosure provides a provisional tibial prosthesis system whichcan be adjusted without removing the bearing component and the bearingsupport from the knee joint and only distracting the knee joint adistance equal to the height of a particular shim. In one embodiment,the shims are available in a variety of heights to vary the spacing ofthe bearing component from the bearing support. In other embodiments,the shims are available in equal heights for shim slacking.

In one embodiment of the present disclosure, a surgeon can space abearing component having a hearing component, height from a bearingsupport by sliding a first shim having a first shim height between thebearing component and the bearing support in the anterior/posteriordirection, and subsequently perform range of motion testing of the kneejoint to verily proper sizing of the provisional tibial prosthesissystem. If the provisional tibial prosthesis system is properly sizedwith the first shim between the bearing component and the beatingsupport, a first final tibial prosthesis represented by the first shimheight and the bearing height can be selected for implantation in thenatural knee. If the provisional tibial prosthesis system is notproperly sized, the surgeon can remove the first shim from between thebearing component and the bearing support in the anterior/posteriordirection, and space the bearing component from the bearing support bysliding a second shim having a second shim height between the bearingcomponent and the bearing support in the anterior/posterior direction.If the provisional tibial prosthesis system is properly sized with thesecond shim between the bearing component and the bearing support, asecond final tibial prosthesis represented by the second shim height andthe bearing height can be selected for implantation in the natural knee.In another embodiment, if the provisional tibial prosthesis system isnot properly sized with the first shim between the bearing component andthe bearing support, a second shim having a second shim height can beused to space the bearing component from the bearing support by slidingthe second shim between the bearing component and the bearing support inthe anterior/posterior direction with the first shim also between thebearing component and the bearing support. If the provisional tibialprosthesis system is properly sized with the first shim and the secondshim between the bearing component and the bearing support, a thirdfinal tibial prosthesis represented by the first shim height, the secondshim height, and the bearing height can be selected for implantation inthe natural knee. This stacking of the shims can be repeated using avariety of shims having equal or varying height.

The disclosure, in one form thereof, comprises a provisional tibialprosthesis system for a prosthetic knee joint for implantation in anatural knee, the provisional tibial prosthesis system capable ofalternatively mimicking the geometry of a first final tibial prosthesisand a second final tibial prosthesis, the natural knee comprising aproximal tibia and a distal femur and having a medial/lateral axis, ananterior/posterior axis, and a proximal/distal axis, the medial/lateralaxis corresponding to a medial/lateral direction, the anterior/posterioraxis corresponding to an anterior/posterior direction, and theproximal/distal axis corresponding to a proximal/distal direction, theprovisional tibial prosthesis system including a tibial base platehaving a bone contacting surface and an opposing base plate superiorsurface; a tibial, bearing component having a tibial bearing componentheight, the tibial bearing component attachable to the tibial baseplate,the tibial bearing component height representing the first final tibialprosthesis; and a shim having a shim height, the shim slidable relativeto both the tibial base plate and the tibial bearing component to beslidably receivable between the tibial base plate and the tibial bearingcomponent in the anterior/posterior direction when the tibial base plateand the tibial bearing component are separated by a distance along theproximal/distal axis equal to the shim height, the shim heightcooperating with the tibial bearing component height to represent thesecond final tibial prosthesis.

The disclosure, in another form thereof, comprises a provisional tibialprosthesis system for a prosthetic knee joint for implantation in anatural knee, the provisional tibial prosthesis system capable ofalternatively mimicking the geometry of a first final tibial prosthesis,a second final tibial prosthesis, and a third final tibial prosthesis,the natural knee comprising a proximal tibia and a distal femur andhaving a medial/lateral axis, an anterior/posterior axis, and aproximal/distal axis, the medial/lateral axis corresponding to amedial/lateral direction, the anterior/posterior axis corresponding toan anterior/posterior direction, and the proximal/distal axiscorresponding to a proximal/distal direction, the provisional tibialprosthesis system including a tibial base plate having a bone contactingsurface and an opposing base plate superior surface; a tibial, beatingcomponent having a tibial bearing component height, the tibial bearingcomponent attachable to the tibial base plate, the tibial bearingcomponent height representing the first final tibial prosthesis; a firstshim having a first shim height, the first shim slidable relative toboth the tibial base plate and the tibial bearing component to beslidably receivable between the tibial base plate and the tibial bearingcomponent in the anterior/posterior direction when the tibial base plateand the tibial bearing component are separated by a first distance alongthe proximal/distal axis equal to the first shim height, the first shimheight cooperating with the tibial bearing component height to representthe second final tibial prosthesis; and a second shim having a secondshim height the second shim slidable relative to both the tibial baseplate and the tibial bearing component to be slidably receivable betweenthe tibial base plate and the tibial bearing component in theanterior/posterior direction when the tibial base plate and the tibialbearing component are separated by a second distance along theproximal/distal axis equal to the first shim height, and the second,shim height, the first shim height and the second shim heightcooperating with the tibial bearing component height to represent thethird final tibial prosthesis.

The disclosure, in a further form thereof, comprises a method ofdetermining a size of a final tibial prosthesis for a prosthetic kneejoint for implantation in a natural knee, the natural knee comprising aproximal tibia and a distal femur and having a medial/lateral axis, ananterior/posterior axis, and a proximal/distal axis, the medial/lateralaxis corresponding to a medial/lateral direction, the anterior/posterioraxis corresponding to an anterior/posterior direction, and theproximal/distal axis corresponding to a proximal/distal direction, themethod including: selecting a provisional tibial prosthesis systemincluding a tibial base plate having a bone contacting surface and anopposing base plate superior surface; a tibial bearing component havinga tibial bearing component height, the tibial bearing componentattachable to the tibial base plate; and a first shim having a firstshim height, the first shim slidable relative to both the tibial baseplate and the tibial bearing component to be slidably receivable betweenthe tibial base plate and the tibial bearing component in theanterior/posterior direction when the tibial base plate and the tibialbearing component are separated by a first distance along theproximal/distal axis equal to the first shim height; resecting theproximal tibia to form a resected proximal tibia surface; positioningthe bone contacting surface of the tibial base plate on the resectedproximal tibia surface; positioning the tibial bearing component on thetibial base plate; and spacing the tibial bearing component from thetibial base plate by sliding the first shim between the tibial baseplate and the tibial bearing component in the anterior/posteriordirection, without distracting the femur from the tibia a distancegreater than the first shim height.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of thisdisclosure, and the manner of attaining them, will become more apparentand the disclosure itself will be better understood by reference to thefollowing descriptions of embodiments of the disclosure taken inconjunction with the accompanying drawings, wherein;

FIG. 1 is an exploded perspective view of a provisional tibialprosthesis system in accordance with an exemplary first embodiment ofthe present disclosure;

FIG. 2A is a plan view of a tibial bearing component of the provisionaltibial prosthesis system of FIG. 1;

FIG. 2B is a front elevation view of the tibial bearing component ofFIG. 2A;

FIG. 2C is a bottom view of the tibial bearing component of FIG. 2A;

FIG. 2D is a cross-sectional view taken along line 2D-2D of FIG. 2A;

FIG. 3A is a plan view of a base component of the provisional tibialprosthesis system of FIG. 1;

FIG. 3B is a front elevation view of the base component of FIG. 3A;

FIG. 3C is a side elevation view of the base component of FIG. 3A;

FIG. 4A is a plan view of a shim of the provisional tibial prosthesissystem of FIG. 1;

FIG. 4B is a front elevation view of the shim of FIG. 4A;

FIG. 4C is a cross-sectional view taken along line 4C-4C of FIG. 4A;

FIG. 5 is a perspective view of a tibial base plate of the provisionaltibial prosthesis system of FIG. 1;

FIG. 6 is a perspective view of a knee joint and the provisional tibialprosthesis system of FIG. 1 illustrating a resected proximal tibiasurface with the tibial base plate of FIG. 5 attached thereon, the basecomponent of FIG. 3A positioned on the tibial base plate, the tibialbearing component of FIG. 2A attached to the base component, and asurgical instrument connected to the shim of FIG. 4A, and illustratingaxes of the knee joint;

FIG. 7 is a perspective view of the provisional tibial prosthesis systemof FIG. 6 illustrating using the surgical instrument of FIG. 6 to slidethe shim between the base component and the tibial bearing component inan anterior/posterior direction;

FIG. 8 is a perspective view of the provisional tibial prosthesis systemof FIG. 6 illustrating the shim between the base component and thetibial bearing component;

FIG. 9 is an exploded, view of a provisional tibial prosthesis system inaccordance with an exemplary second embodiment of the presentdisclosure;

FIG. 10A is a plan view of a provisional tibial prosthesis system inaccordance with an exemplary third embodiment of the present disclosure;

FIG. 10B is a cross-sectional view taken along line 10B-10B of FIG. 10A;

FIG. 10C is a cross-sectional view taken along line 10C-10C of FIG. 10A;

FIG. 11A is a plan view of a provisional tibial prosthesis system inaccordance with an exemplary fourth embodiment of the presentdisclosure;

FIG. 13B is a front elevation view of the provisional tibial prosthesissystem of FIG. 31A;

FIG. 12A is an exploded view of a provisional tibial prosthesis systemin accordance with an exemplary fifth embodiment of the presentdisclosure;

FIG. 12B is a front elevation view of the provisional tibial prosthesissystem of FIG. 12A;

FIG. 12C is a cross-sectional view taken along line 12C-12C of FIG. 12B;

FIG. 13A is a plan view of a provisional tibial prosthesis system inaccordance with an exemplary sixth embodiment of the present disclosure;

FIG. 13B is a cross-sectional view taken along line 13B-13B of FIG. 13A;

FIG. 14 is a partial perspective view of a provisional tibial prosthesissystem in accordance with an exemplary seventh embodiment of the presentdisclosure;

FIG. 15 is a perspective view of a provisional tibial prosthesis systemin accordance with an exemplary eighth embodiment of the presentdisclosure;

FIG. 16A is a perspective view of a provisional tibial prosthesis systemin accordance with an exemplary ninth embodiment of the presentdisclosure;

FIG. 16B is a plan view of the provisional tibial prosthesis system ofFIG. 16A;

FIG. 16C is a cross-sectional view taken along line 16C-16C of FIG. 16B;

FIG. 17A is a perspective view of a provisional tibial prosthesis systemin accordance with an exemplary tenth embodiment of the presentdisclosure;

FIG. 17B is a cross-sectional view taken along line 17B-37B of FIG. 37A;

FIG. 17C is a cross-sectional view taken along line 17C-17C of FIG. 17A;

FIG. 18A is a perspective view of a provisional tibial prosthesis systemin accordance with an exemplary eleventh embodiment of the presentdisclosure;

FIG. 18B is a partial cross-sectional view taken along line 18B-18B ofFIG. 18A;

FIG. 19A is a plan view of a tibial bearing component in accordance withanother exemplary embodiment of the present disclosure;

FIG. 19B is a front elevation view of the tibial bearing component ofFIG. 19A;

FIG. 19C is a plan view of a shim in accordance with another exemplaryembodiment of the present disclosure;

FIG. 19D is a front elevation view of the shim of FIG. 19C; and

FIG. 19E is a cross-sectional view taken along line 19E-19E of FIG. 19Aillustrating the shim of FIG. 19C positioned within a recess of thetibial bearing component of FIG. 19A.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate exemplary embodiments of the disclosure, and suchexemplifications are not to be construed as limiting the scope of thedisclosure in any manner.

DETAILED DESCRIPTION

The present disclosure provides a provisional tibial prosthesis systemfor a set of prosthetic knee joints for implantation in a natural knee,the provisional tibial prosthesis system including a bearing componentand a beating support, the spacing of the beating component from thebearing support is adjustable to allow for representation of a varietyof different sized final tibial prostheses.

The provisional tibial prosthesis system of the present disclosure maybe used with a final tibial prosthesis in accordance with the tibialprosthesis described in U.S. Patent Application Ser. No. 61/381,800,filed Sep. 10, 2010, entitled “Tibial Prosthesis Facilitating RotationalAlignment,” the entire disclosure of which is hereby expresslyincorporated herein by reference. Further, the provisional tibialprosthesis system of the present disclosure may be used with the methodand apparatus described in U.S. Patent Application Ser. No. 61/424,222,filed Dec. 17, 2010, entitled “User Interface Related to a SurgicalProvisional,” the entire disclosure of which was previously incorporatedherein by reference.

FIG. 6 illustrates a natural knee comprising proximal tibial T anddistal, femur F. FIG. 6 depicts a coordinate system of the natural kneeincluding anterior/posterior axis A_(A-P), medial/lateral axis A_(M-L),and proximal/distal axis A_(A-D). Anterior/posterior axis A_(A-P)corresponds to anterior/posterior direction 20, medial/lateral axisA_(M-L) corresponds to medial/lateral direction 22, and proximal/distalaxis A_(P-D) corresponds to proximal/distal direction 24.Anterior/posterior direction 20, medial/lateral direction 22, andproximal/distal direction 24 are each normal to one another. As usedherein, “proximal” refers to a direction generally toward the heart of apatient, and “distal” refers to the opposite direction of proximal,i.e., away from the heart of the patient. Further, as used herein,“anterior” refers to a direction generally toward the front of apatient, and “posterior” refers to the opposite direction of anterior,i.e., toward the back of a patient. As used herein, “medial” refers to adirection generally toward the middle of a patient, and “lateral” refersto the opposite direction of medial, i.e., toward the side of a patient.For purposes of this disclosure, the above-mentioned anatomicalreferences are used in the description of the components of theprovisional tibial prosthesis system with reference to a desiredoperable use of the components in the body.

While the exemplary embodiments detailed herein are shown and describedwith regard to a left knee, it will be appreciated that the presentdisclosure is equally applicable to a right knee configuration.

The disclosed embodiments of the present disclosure include a tibialbearing component and a base component. For example, as shown in FIG. 1of an exemplary first embodiment, provisional tibial prosthesis system30A includes tibial bearing component 32A and base component 34A.Reference numbers for the provisional tibial prosthesis system, thetibial bearing component, and the base component utilize the samenumerical reference number combined with different letters todistinguish the exemplary embodiment (i.e., tibial bearing component32A, 32B, 32C, etc. respectively correspond to the first, second, andthird exemplary embodiments, etc.). For the purposes of this disclosure,a reference numeral followed by A-K corresponds to a similar featurebetween the exemplary first through eleventh embodiments, respectively.

The common elements between the eleven described exemplary embodimentsfollow a similar reference number labeling scheme. For example, thefirst exemplary embodiment, as illustrated in FIGS. 2A-2D, includestibial bearing component 32A generally including tibial beatingcomponent inferior surface 42A, opposing tibial bearing componentsuperior surface 44A, and tibial bearing component peripheral wall 46Aextending from inferior surface 42A to superior surface 44A. Tibialbearing component 32A includes bearing anterior side 48A, bearingposterior side 50A, bearing lateral side 52A, and bearing medial side54A. Superior surface 44A is adapted to articulate with condyles of adistal femur F (shown in FIGS. 6-8), or condyles of a femoral component(not shown) secured to a distal end of a femur. Superior surface 44Aincludes bearing lateral articular surface 56A in bearing lateral side52A and bearing medial articular surface 58A in bearing medial side 54A,with central tibial eminence 60A disposed between bearing articularsurfaces 56A, 58A. Referring to FIG. 2A, eminence 60A generallycorresponds in shape and size with the natural tibial eminence of aproximal tibial T (shown in FIGS. 6-8) prior to resection. Tibialbearing component 32A further includes PCL cut-out 62A disposed atposterior side 50A between lateral articular surface 56A and medialarticular surface 58A, PCL cut-out 62A is sized and positioned tocorrespond with a posterior cruciate retaining ligament of a knee joint.

In the exemplary embodiment of FIGS. 2A-2D, tibial bearing component 32Ais illustrated as a cruciate retaining bearing component though it iscontemplated that other tibial bearing components may be utilized inaccordance with the present disclosure such as bearing components whichcooperate to form a posterior stabilized prosthesis or a knee prosthesishaving an intermediate level of constraint between a posteriorstabilized and cruciate retaining prosthesis. Tibial bearing component32A may also be made available in a variety of shapes and sizes toaccommodate a variety of knee joints.

As shown in FIGS. 2A-2D, tibial bearing inferior surface 42A of tibialbearing component 32A includes slots 64A, alignment pins 68A, bearingcavity 70A, and beating nub cavities 72A. As illustrated in FIGS. 2B and2C, slots 64A are exposed at anterior side 48A and extend from anteriorside 48A toward posterior side 50A within tibial bearing component 32Ain a direction parallel to anterior/posterior axis A_(A-P). As shown inFIG. 2B, in an exemplary embodiment, slots 64A have tapering walls 66A.Referring to FIGS. 2B and 2C, alignment pins 68A are located betweenslots 64A at anterior side 48A. Bearing cavity 70A extends from inferiorsurface 42A towards superior surface 44A and is sized to acceptprotrusion 96A (shown in FIG. 3A) of base component 34A. Further,bearing cavity 70A includes bearing nub cavities 72A which extend onopposing sides of bearing cavity 70A and are each sized to receive a nub104A (shown in FIG. 3A) located on protrusion 96A of base component 34A.

The first exemplary embodiment, as illustrated in FIGS. 3A-3C, alsoincludes base component 34A generally including base component inferiorsurface 82A, opposing base component superior surface 84A, and basecomponent peripheral wall 86A extending from inferior surface 82A tosuperior surface 84A. Base component 34A includes base anterior side88A, base posterior side 90A, base lateral side 92A, and base medialside 94A.

Base component 34A includes protrusion 96A extending from superiorsurface 84A. Protrusion 96A includes nubs 104A which extend on opposingsides of protrusion 96A. Referring to FIG. 3B, protrusion bottom wall100A spans the distance between protrusion 96A and superior surface 84A.Further, protrusion 96A and bottom wall 100A define bottom wallindentations 102A between protrusion 96A and superior surface 84A. Basecomponent 34A also includes notch 106A at posterior side 90A having agenerally W-shape, undercut portion 108A, medial side groove 110A, andlateral side groove 112A.

FIG. 5 illustrates tibial base plate 38A according to an exemplaryembodiment of the present disclosure. Tibial base plate 38A generallyincludes base plate superior surface 150A and opposing base plate bonecontacting surface 152A. Tibial base plate 38A closely corresponds insize and shape with the resected proximal tibia surface, and includesbase plate peripheral wall 156A extending from bone contacting surface152A to superior surface 150A. Base plate peripheral wall 156A includesraised perimeter 158A and tibial base plate 38A includes base plateanterior side 166A, base plate posterior side 168A, base plate medialside 170A, and base plate lateral side 172A. Superior surface 150Aincludes medial condylar portion 160A and lateral condylar portion 162A.Base plate 38A further includes PCL cut-out 164A disposed at posteriorside 168A between medial condylar portion 160A and lateral condylarportion 162A to allow a posterior cruciate retaining ligament of a kneejoint to pass therethrough. Further, tibial base plate 38A includes boss174A having boss medial sides 176A and boss lateral sides 178A. Further,an interior recess is formed between inner medial side 176A and innerlateral side 178A.

The manner in which tibial base plate 38A is attached to a proximaltibia will now be discussed. The proximal portion of a patient's tibiais resected to provide a substantially fiat surface for receipt of bonecontacting surface 152A of tibial base plate 38A. Once the proximaltibia is resected, tibial base plate 38A is implanted and secured to theresected proximal tibia using standard surgical techniques. For example,conventional features such as a stem and fins may be located on bonecontacting surface 152A to affect securement of tibial base plate 38A toa proximal tibia. While tibial base plate 38A is part of the provisionalprosthesis system disclosed herein, tibial base plate 38A may also bepart of a final prosthesis system, i.e., tibial base plate 38A is thefinal base plate implanted to a resected proximal tibia. Tibial baseplate 38A may also be part of any other tibia contacting implementutilized in knee arthroplasty. For example, tibial base plate 38A couldbe part of a tibial sizing plate system in accordance with the tibialsizing plate described in U.S. Pat. No. 7,850,698, issued Dec. 14, 2010,entitled “Tibial Trialing Assembly and Method of Trialing a TibialImplant,” the entire disclosure of which is hereby expresslyincorporated herein by reference. Tibial base plate 38A may also be partof a tibial sizing plate system in accordance with the tibial sizingplate described in two brochures published by Zimmer, Inc., namely the“Zimmer® Patient Specific Instruments, Surgical Techniques for NexGen®Complete Knee Solution” brochure, copyright 2010, and the “Zimmer®NexGen Trabecular Metal Tibial Tray, Surgical Technique” brochure,copyright 2007 and 2009, the entire disclosures of which are herebyexpressly incorporated herein by reference.

In an exemplary embodiment, as illustrated in FIGS. 6-8, base component34A is secured to tibial base plate 38A by positioning base componentinferior surface 82A on base plate superior surface 150A. Undercutportion 108A (shown in FIGS. 3B and 3C) of base component 34A ispositioned within raised perimeter 158A (shown in FIG. 5) of base plateperipheral wall 156A. Raised perimeter 158A acts as a physical barrierto prevent base component 34A from significant relative movementrelative to tibial base plate 38A in medial/lateral direction 22 andanterior/posterior direction 20. In this embodiment, base component 34Ais movable relative to tibial base plate 38A in proximal/distaldirection 24. In one embodiment, base component 34A is sized to haveclearance with tibial base plate 38A, i.e., some movement between basecomponent 34A and tibial base plate 38A in medial/lateral direction 22and anterior/posterior direction 20 is allowable, but base component 34Aand tibial base plate 38A are prohibited from disengagement inmedial/lateral direction 22 and anterior/posterior direction 20.

In another exemplary embodiment, tibial bearing component 32A ispositioned atop tibial base plate 38A. In such an embodiment, bearinginferior surface 42A (shown in FIG. 2C) of bearing component 32A ispositioned within raised perimeter 158A of base plate peripheral wall156A in a manner similar to the attachment between base component 34Aand tibial base plate 38A discussed above. Raised, perimeter 158A againacts as a physical barrier to prevent bearing component 32A fromsignificant relative movement relative to tibial base plate 38A inmedial/lateral direction 22 and anterior/posterior direction 20. In thisembodiment, bearing component 32A is movable relative to tibial baseplate 38A in proximal/distal direction 24. In one embodiment, bearingcomponent 32A is sized to have clearance with tibial base plate 38A,i.e., some movement between bearing component 32A and tibial base plate38A in medial/lateral direction 22 and anterior/posterior direction 20is allowable, but bearing component 32A and tibial base plate 38A areprohibited from disengagement in medial/lateral direction 22 andanterior/posterior direction 20.

For the purposes of this disclosure, any of the disclosed exemplaryfirst through eleventh embodiments are attachable to a tibial base platesuch as tibial base plates 38A, 38B respectively shown in FIGS. 5 and 9.It is also contemplated that other tibial base plates having a varietyof different sizes and shapes can be used in accordance with theprovisional tibial prosthesis systems of the present disclosure.

Referring to FIGS. 1-3C, the attachment of tibial bearing component 32Ato base component 34A will now be described. Tibial bearing component32A is positioned atop base component 34A by positioning protrusion 96Aof base component 34A within bearing cavity 70A of tibial bearingcomponent 32A and positioning nubs 104A of protrusion 96A respectivelywithin bearing nub cavities 72A. In such an embodiment, base component34A is locked to tibial bearing component 32A in medial/lateraldirection 22 when, protrusion 96A is received within, bearing cavity 70Aand base component 34A is locked to tibial beating component 32A inanterior/posterior direction 20 when nubs 104A are respectively receivedwithin nub cavities 72A. The walls of bearing cavity 70A provide aphysical barrier to prevent significant relative movement between basecomponent 34A and tibial bearing component 32A in medial/lateraldirection 22 and the walls of nub cavities 72A provide a physicalbarrier to prevent significant relative movement between base component34A and tibial bearing component 32A in anterior/posterior direction 20.When tibial bearing component 32A is positioned atop base component 34A,tibial bearing component 32A is movable relative to base component 34Ain proximal/distal direction 24. In this embodiment, as illustrated inFIGS. 6-8, base component 34A is secured to tibial base plate 38A andbase component 34A is located between tibial bearing component 32A andtibial base plate 38A. In another embodiment, as discussed above, tibialbearing component 32A can be positioned directly atop tibial base plate38A.

FIGS. 4A-4C illustrate shim 36A according to an exemplary embodiment ofthe present disclosure. Shim 36A generally includes shim inferiorsurface 122A, opposing shim superior surface 124A, and shim peripheralwall 126A extending from inferior surface 122A to superior surface 124A.Shim peripheral wall 126A defines a shim exterior profile. In oneembodiment, the shim exterior profile substantially matches the tibialbase plate exterior profile. Shim 36A also includes shim anterior side128A, shim posterior side 130A, shim lateral side 132A, and shim medialside 134A. As shown in FIGS. 4A-4C, shim superior surface 124A includesrails 136A and handle alignment rails 142A. As illustrated in FIGS. 4Aand 4B, rails 136A extend from anterior side 128A toward posterior side130A parallel to anterior/posterior axis A_(A-P) (shown in FIG. 6). Inan exemplary embodiment, rails 136A have lead-in edges 140A and taperedwalls 138A. Handle alignment rails 142A are located between rails 136Aat anterior side 128A. Further, between handle alignment rails 142A isshim ramp 148A. Shim 36A also includes shim notch 144A and lead-in walls146A, i.e., tapering posterior walls, at posterior side 130A foraligning shim 36A and guiding-insertion of shim 36A inanterior/posterior direction 20, as will be further described below.

In an exemplary embodiment, a set of a plurality of shims 36A can beprovided to allow for varying levels of adjustment of provisional tibialprosthesis system 30A, i.e., increasing the distance between tibialbearing component 32A and base component 34A by the shim height of aparticular shim 36A inserted therebetween. For example, if fourdifferent sizes were to be used in the set of shims, the height of theshims could be 1 mm, 2 mm, 3 mm, and 4 mm. In another embodiment, a setof shims could include a plurality of shims having equal sizes forstacking shims. The stacking shims embodiment can also include aplurality of shims having varying heights. It is envisioned that the setof a plurality of different sized shims 36A could include any desirednumber of different sized shims having any number of shim heights.

During insertion of shim 36A, as best shown in FIGS. 6 and 7, lead-inwalls 146A of shim 36A are placed between bearing component 32A and basecomponent 34A and are used to affect separation of bearing component 32Afrom base component 34A by a distance along proximal/distal axis A_(P-D)equal to a height of shim 36A. In this manner, lead-in walls 146A act asa ramp to separate bearing component 32A from base component 34A.Advantageously, the provisional tibial prosthesis system of the presentdisclosure can be adjusted in a manner requiring the knee joint to onlybe distracted by a distance equal to the height of shim 36A. In anotherembodiment, to further help separation of bearing component 32A frombase component 34A, bearing component inferior surface 42A (shown inFIG. 2C) at bearing anterior side 48A (shown in FIGS. 2A-2C) can includea beveled edge corresponding to lead-in walls 346A of shim 36A.

As illustrated in FIGS. 6-8, in one exemplary embodiment, shim 36A isslidably receivable between tibial bearing component 32A and basecomponent 34A in anterior/posterior direction 20. The insertion of shim36A between tibial bearing component 32A and base component 34A inanterior/posterior direction 20 allows tibial bearing component 32A toonly be separated from, base component 34A by a distance alongproximal/distal axis A_(P-D) equal to the height of shim 36A. Also,tibial, bearing component 32A and base component 34A of provisionaltibial prosthesis system 30A do not have to be removed from the kneejoint to insert and remove shims 36A.

In an alternative embodiment, base component 34A is not utilized andshim 36A is positioned between bearing component 32A and base plate 38A.In this embodiment, tibial bearing component 32A is positioned atoptibial base plate 38A such that bearing inferior surface 42A (shown inFIG. 2C) of bearing component 32A is positioned within raised perimeter158A of base plate peripheral wall 156A. Referring to FIG. 5, in such anembodiment, the anterior rail of base plate 38A will be missing to allowshim 36A to be slidably receivable between tibial bearing component 32Aand tibial base plate 38A in anterior/posterior direction 20 usinglead-in walls 146A of shim 36A to separate tibial bearing component 32Afrom tibial base plate 38A by a distance along proximal/distal axisA_(P-D) equal to a height of shim 36A. In this embodiment, shim 36A willhave a perimeter configured to allow shim 36A to be positioned to thesecurement features of base plate 38A. For example, shim 36A will have aperimeter similar to the perimeter of base component 34A (shown in FIG.3A).

As previously discussed, when tibial bearing component 32A is positionedatop base component 34A, tibial bearing component 32A is movablerelative to base component 34A in proximal/distal direction 24. In theexemplary first embodiment, shim 36A takes away this last degree offreedom between tibial bearing component 32A and base component 34A,i.e., when shim 36A is received between base component 34A and tibialbearing component 32A, shim 36A locks tibial bearing component 32A tobase component 34A in proximal/distal direction 24, i.e., significantrelative movement between tibial bearing component 32A and basecomponent 34A in proximal/distal direction 24 is prevented.

The manner in which shim 36A locks tibial bearing component 32A to basecomponent 34A in proximal/distal direction 24 will now be discussed.Referring to FIGS. 6-8, shim 36A is inserted between tibial bearingcomponent 32A and base component 34A in anterior/posterior direction 20.Referring to FIGS. 2A-2D and 4A-4C, and 6, shim rails 136A are alignedwith respective tibial bearing component slots 64A. Referring to FIG.4A, rails 136A each include lead-in edge 140A to guide insertion ofrails 136A in slots 64A. The rail/slot connection between shim 36A andtibial bearing component 32A is important because it prevents lift-offof tibial bearing component 32A from shim 36A, i.e., preventssignificant relative movement, between tibial bearing component 32A andshim 36A in proximal/distal direction 24. In one exemplary embodiment,as shown in FIGS. 2A-2D and 4A-4C, slots 64A of tibial bearing component32A and rails 136A of shim 36A each have a dovetail cross-sectionalshape. Slots 64A including tapering walls 66A of bearing component 32Acooperate with rails 136A having tapering walls 138A of shim 36A to actas a physical barrier to prevent lift-off of the tibial bearingcomponent 32A from shim 36A. In an alternate embodiment, slots 64A oftibial bearing component 32A and rails 136A of shim 36A can each have aT-shaped cross-sectional shape or other various shapes that wouldprovide a physical barrier that would prevent lift-off, i.e., preventsignificant relative movement between tibial bearing component 32A andbase component 34A in proximal/distal direction 24, or any movement oftibial bearing component 32A in any direction that is perpendicular tobase component 34A.

Referring to FIGS. 3A-4C, as shim 36A is inserted in anterior/posteriordirection 20 between tibial bearing component 32A and base component 34Ausing lead-in walls 146A as discussed above, shim 36A also locks to basecomponent 34A by shim notch 144A formed in shim posterior side 130Aattaching to base component 34A by sliding notch 144A in indentations102A between protrusion 96A and base component superior surface 84A.This shim connection between shim 36A and base component 34A and therail/slot connection between shim 36A and tibial bearing component 32Aallows shim 36A to lock tibial bearing component 32A to base component34A in proximal/distal direction 24.

Referring to FIGS. 19A-19E, an alternate embodiment including tibialbearing component 32A and shim 36L is illustrated. Tibial bearingcomponent 32L and shim 36L respectively include similar components totibial bearing component 32A illustrated in FIGS. 2A-2D and shim 36Aillustrated in FIGS. 4A-4C. For the sake of brevity, these similarcomponents will not all be discussed, in conjunction with the alternateembodiments disclosed in FIGS. 19A-19E. Referring to FIGS. 19A and 19B,tibial bearing component 32L includes recess 78L extending from bearingcomponent inferior surface 42L towards bearing component superiorsurface 44L. Recess 78L is sized to receive shim 36L (shown in FIGS. 19Cand 19D). FIG. 19E illustrates shim 36L received in recess 78L of tibialbearing component 32L. Referring to FIGS. 19A and 19C, shim rails 136Lare aligned with respective tibial component slots 64L. Rails 136L ofshim 36L each include lead-in edge 140L to guide insertion of rails 136Lin slots 64L of tibial bearing component 32L. Shim 36L is inserted inrecess 78L of tibial bearing component 32L in anterior/posteriordirection 20 (shown in FIG. 6). In one embodiment, the height of shim36L is equal to the height of recess 78L of tibial bearing component32L. In other embodiments, the height of shim 36L could be less than theheight of recess 78L. In this embodiment, shim 36L locks tibial bearingcomponent 32L to shim 36L in proximal/distal direction 24 (shown in FIG.6) without spacing tibial bearing component 32L from a base component,i.e., either base component 34A (shown in FIGS. 3A-3C), tibial baseplate38A (shown in FIG. 5), or other tibia contacting implement utilized inknee arthroplasty.

Before shim 36L is inserted between tibial bearing component 32L andbase component 34A (shown in FIGS. 3A-3C), tibial bearing component 32Lis positioned on base component 34A. With, tibial bearing component 32Lpositioned on base component 34A, recess 78L spaces tibial bearingcomponent 32L from base component 34A a distance along proximal/distalaxis A_(P-D) (shown in FIG. 6) at least equal to the height of shim 36L.Referring to FIGS. 3A-3C, 19A and 19E, in one embodiment, tibial bearingcomponent 32L can be positioned on base component 34A by positioningprotrusion 96A of base component 34A within bearing cavity 70L of tibialbearing component 32L and positioning nubs 304A of protrusion 96Arespectively within bearing nub cavities 72L. Subsequently, shim 36L canbe inserted between tibial bearing component 32L and base component 34Ain anterior/posterior direction 20 (shown in FIG. 6). With shim 36Linserted within recess 78L of tibial bearing component 32L, shim 36Lprevents significant relative movement between tibial bearing component32L and base component 34A in proximal/distal direction 24 (shown inFIG. 6) without spacing tibial bearing component 32L from base component34A. Referring to FIGS. 19B and 19E, because shim 36L is received inrecess 78L of tibial bearing component 32L, the height of shim 36Lcooperates with the height of tibial bearing component 32L to representa first final tibial prosthesis without shim 36L adding to the height oftibial bearing component 32L.

Referring to FIGS. 6-8, an illustrative procedure in accordance with thepresent disclosure to determine the size of a final tibial prosthesisfor a prosthetic knee joint for implantation in a natural knee will nowbe described. In one embodiment, a surgeon selects a provisional tibialprosthesis system, such as provisional tibial prosthesis system 30A,having tibial base plate 38A (shown in FIG. 5) having bone contactingsurface 152A and opposing base plate superior surface 150A, tibialbearing component 32A having a tibial bearing component height, tibialbearing component 32A attachable to tibial base plate 38A, and shim 36Ahaving a shim height, shim 36A slidably receivable between tibial baseplate 38A and tibial bearing component 32A in anterior/posteriordirection 20 when tibial base plate 38A and tibial bearing component 32Aare separated by a distance along proximal/distal axis A_(P-D) equal tothe shim height.

Next, the proximal portion of a patient's tibia is resected usingstandard surgical techniques to provide a substantially flat surface forreceipt of bone contacting surface 152A of tibial base plate 38A. Oncethe proximal tibia is resected, tibial baseplate 38A is implanted andsecured to the resected proximal tibia. Subsequently, tibial bearingcomponent 32A corresponding to the constraint level chosen by thesurgeon is positioned atop tibial base plate 38A such that bearinginferior surface 42A (shown in FIG. 2C) of bearing component 32A ispositioned within raised perimeter 158A (shown in FIG. 5) of base plateperipheral wall 156A. If base component 34A is utilized, base component34A is positioned atop tibial base plate 38A between bearing component32A and base plate 38A.

The surgeon can then perform range of motion testing of the knee jointto verify proper sizing of the provisional tibial prosthesis system. Ifa surgeon determines that a provisional tibial prosthesis system, isproperly sized with tibial bearing component 32A positioned atop tibialbase plate 38A, a first final tibial prosthesis can be selected whichcorresponds to the height of tibial bearing component 32A. If theprovisional tibial prosthesis system is determined to not be properlysized, tibial bearing component 32A can be spaced from tibial base plate38A by sliding shim 36A having a first shim height, e.g., 1 mm, betweentibial base plate 38A and tibial bearing component 32A inanterior/posterior direction 20.

The surgeon can then perform range of motion testing of the knee jointto verify proper sizing of the provisional tibial prosthesis system withshim 36A having a first shim height inserted between tibial bearingcomponent 32A and tibial base plate 38A. If the provisional tibialprosthesis system is determined by the surgeon to be properly sized withshim 36A having first shim height between bearing component 32A andtibial base plate 38A, the surgeon can select a second final tibialprosthesis represented by the first shim height and the tibial bearingcomponent height.

In one embodiment, if the provisional tibial prosthesis system is notproperly sized after insertion of shim 36A having the first shim height,e.g., 1 mm, the 1 mm shim 36A can be removed in anterior/posteriordirection 20, another shim 36A may be selected having a second height,e.g., 2 mm, and tibial bearing component 32A can then be spaced fromtibial base plate 38A by sliding shim 36A having the second shim heightbetween tibial base plate 38A and tibial bearing component 32A inanterior/posterior direction 20. If the provisional tibial prosthesissystem is determined by the surgeon to be properly sized with shim 36Ahaving second shim height, e.g., 2 mm, the surgeon can select a thirdfinal tibial prosthesis represented by the second shim height and thetibial bearing component height.

In an alternate embodiment, after inserting shim 36A having a first shimheight, e.g., 1 mm, if a surgeon determines that the provisional tibialprosthesis system with shim 36A having the first shim height is notproperly sized, shim 36A having a height of 1 mm can be left betweentibial base plate 38A and tibial bearing component 32A, and a secondshim 36A having a second shim height, e.g., 1 mm, can be inserted inanterior/posterior direction 20 between tibial base plate 38A and tibialbearing component 32A to separate tibial bearing component 32A fromtibial base plate 38A by a distance along proximal/distal axis A_(P-D)equal to the first shim, height and the second shim height. In thisembodiment, shim 36A may not include either the securement featuresdiscussed above that lock shim 36A to tibial bearing component 32A orthe securement features discussed above that lock shim 36A to basecomponent 34A. For example, referring to FIGS. 4A and 4B, shim 36A maynot include rails 136A so that tibial bearing component 32A can moverelative to shim 36A in proximal/distal direction 24 (shown in FIG. 6)when shim 36A is inserted between base plate 38A and bearing component32A. In this manner, a second shim can be inserted in anterior/posteriordirection 20 between base plate 38A and bearing component 32A with afirst shim already positioned between base plate 38A and bearingcomponent 32A.

If the provisional prosthesis system is determined by the surgeon to beproperly sized with both shims 36A inserted, the surgeon can select athird final tibial prosthesis represented by the first shim height, thesecond shim height, and the tibial bearing component height. Thisstacking of the shims can be repeated using a variety of different sizedshims and a variety of different numbered shims for a surgeon todetermine the proper thickness of a provisional tibial prosthesissystem. In an alternative embodiment, several shims all having the sameheight can be used in series to adjust the spacing of bearing component32A from base plate 38A.

Referring to FIGS. 6-8, the use of surgical instrument 180 to insertshim 36A will now be described. FIGS. 6-8 illustrate surgical instrument180 for insertion or removal of shim 36A. Surgical instrument 180generally includes handle body 182, handle end 184, opposing attachmentend 186, alignment pins 188, tooth 190, button 192, and handle pegs 194.Surgical instrument 180 has one alignment pin 188 on each side of tooth190. Alignment pins 188 fit in respective exterior circular recesses inrails 142A (shown in FIG. 4B) of shim 36A to properly align surgicalinstrument 180 to shim 36A. Once properly aligned, tooth 190 of surgicalinstallment 180 slides along shim ramp 148A (shown in FIGS. 4A and 4B)and, when tooth 190 slides past shim ramp 148A, a biasing force on tooth190 causes tooth 190 to travel downward and engage the backside of shimramp 148A to lock surgical instrument 180 to shim 36A. In oneembodiment, a biasing force is exerted on tooth 190 by a tension spring.When surgical instrument 180 is properly locked to shim 36A, a surgeonholding handle end 184 of surgical Instrument 180 can insert shim 36A inanterior/posterior direction 20 between tibial bearing component 32A andtibial base plate 38A to space tibial bearing component 32A from tibialbase plate 38A along proximal/distal axis A_(P-D) a distance equal tothe shim height. Once shim 36A is properly inserted between tibialbearing component 32A and tibial base plate 38A, release button 192 ofsurgical, instrument 180 can be depressed to overcome the biasing forceof the spring to release and disengage tooth 190 from the backside ofshim ramp 148A. Thereafter, surgical instrument 180 can be removed. Inanother embodiment surgical instrument 180 can be used in the mannerdescribed above to insert shim 36A in anterior/posterior direction 20between tibial bearing component 32A and base component 34A. Also,surgical instrument 180 may be used to remove shim 36A from betweentibial bearing component 32A and base component 34A.

Once the proximal portion of a patient's tibia is resected and thetibial prosthesis components of the present disclosure are secured tothe resected proximal tibia, soft tissue balancing of the knee can beperformed. Subsequently, a sizing guide can be attached to the tibialprosthesis components. Similar to the attachment of surgical instrument180 to shim 36A, the sizing guide can include alignment pins that fit inrespective exterior circular recesses in rails 142A (shown in FIG. 4B)of shim 364 to properly align the sizing guide to shim 36A. Onceproperly aligned, a locking component of the sizing guide can slidealong shim ramp 148A (shown in FIGS. 4A and 4B) and, when the lockingcomponent slides past shim ramp 148A, a biasing force on the lockingcomponent can cause the locking component to travel downward and engagethe backside of shim ramp 148A to lock the sizing guide to shim 36A.Similarly, a cut guide such as a femoral finishing cut guide can beattached to shim 36A.

FIG. 9 illustrates an exemplary second embodiment. The severalembodiments of the present disclosure include similar components to theembodiment illustrated in FIGS. 1-8. For the sake of brevity, thesesimilar components will not all be discussed in conjunction with thevarious alternative embodiments disclosed herein. Exemplary secondembodiment provisional tibial prosthesis system 30B includes tibialbearing component 32B, base component 348, shim component 36B, andtibial base plate 38B. In one embodiment, tibial bearing component 32Bis positioned atop base component 34B in a manner similar to thearrangement of tibial bearing component 32A to base component 34Adiscussed above. For example, protrusion 96B is similar to protrusion96A (shown in FIGS. 3A-3C), and bearing cavity 70A (shown in FIGS. 2Cand 2D) is similar to a cavity (not shown) in bearing component inferiorsurface 42B. Similar to the arrangement of protrusion 96A of basecomponent 34A and bearing cavity 70A of bearing component 32A, bearingcomponent 32B is positioned atop base component 34B by positioningprotrusion 96B of base component 34B within a bearing cavity in inferiorsurface 42B of bearing component 32B to lock bearing component 32B tobase component 34B in medial/lateral direction 22 and anterior/posteriordirection 20. Similar to the exemplary first embodiment, shim 36B isslidably receivable between tibial bearing component 32B and basecomponent 34B in anterior/posterior direction 20. As in the exemplaryfirst embodiment, a set of different sized shims 36B can be provided toallow for varying levels of adjustment of provisional tibial prosthesissystem 30B, i.e., increasing the distance between tibial bearingcomponent 32B and base component 34B by the shim height of a particularshim 36B inserted therebetween.

Referring to FIG. 9, shim superior surface 124B includes lateralalignment bump 139B and medial alignment bump 141B which respectivelycooperate with lateral alignment bump 116B and medial alignment bump114B of base component 34B to align shim 36B and guide insertion of shim36B in anterior/posterior direction 20. During insertion of shim 36B,alignment bumps 139B, 141B are placed between bearing component 32B andrespective alignment bumps 114B, 116B of base component 34B and are usedto affect separation of bearing component 32B from base component 34B bya distance along proximal/distal axis A_(P-D) equal to a height of shim368. Alignment bumps 139B, 141B of shim 36B and alignment bumps 114B,116B of base component 34B each include a protrusion portion, on aproximal side and a recessed portion on a distal side.

In one embodiment, the insertion end of shim 36B could include lead-inwalls similar to lead-in walls 146A (shown in FIGS. 4A and 4C) to act asa ramp to separate bearing component 32B from base component 34B.Further, every embodiment of the present disclosure including a shimcomponent slidably insertable between a bearing component and a bearingsupport could include an insertion end having a lead-in wall to act as aramp to separate the bearing component from the bearing support.

Instead of the rail/slot connection system of the first exemplaryembodiment, in the exemplary second, embodiment, shim 36B includeslocking tabs 137B located at shim anterior side 128B. Upon insertion ofshim 368 between tibial bearing component 32B and base component 34B,shim 36B respectively locks shim 36B to tibial bearing component 32B bya first tab 137B engaging in notch 74B of tibial bearing component 32Band locks shim 36B to base component 34B by a second tab 137B engagingbase component 34B at anterior side 88B. In this manner, shim 36B takesaway the last degree of freedom between tibial bearing component 32B andbase component 34B, i.e., when shim 36B is received between basecomponent 34B and tibial bearing component 32B, shim 36B limits movementbetween tibial bearing component 32B and base component 34B inproximal/distal direction 24. In such an embodiment, a surgeon can grasptabs 137B to insert or remove shim 36B from bearing component 32B andbase component 34B. Alternatively, a surgeon can use a standard surgicalinstrument for insertion or removal of shim 36B.

In an alternative embodiment, base component 34B is not utilized andshim 36B is positioned between bearing component 32B and base plate 38B.Referring to FIG. 9, in such an embodiment, the anterior rail of baseplate 388 will be missing to allow shim 36B to be slidably receivablebetween tibial base plate 38B and tibial bearing component 32B inanterior/posterior direction 20.

In another embodiment, after inserting shim 36B having a first shimheight, e.g., 1 mm, if a surgeon determines that the provisional tibialprosthesis system with shim 36B having the first shim height is notproperly sized, shim 36B having a height of 1 mm can be left betweenbase plate 38B and tibial bearing component 32B, and a second shimhaving a second shim height, e.g., 1 mm, can be inserted between baseplate 38B and bearing component 32B to separate bearing component 32Bfrom base plate 38B by a distance along proximal/distal axis A_(P-D)equal to the first shim height and the second shim height. In thisembodiment, shim 36B will not include tabs 137B so that bearingcomponent 32B can move relative to shim 36B in proximal/distal direction24 (shown in FIG. 6) when shim 36B is inserted between base plate 38Band bearing component 32B. In this manner, a second shim can be insertedin anterior/posterior direction 20 between base plate 38B and bearingcomponent 328 with a first slum already positioned between base plate38B and bearing component 32B. In the embodiment including shim 36B withno tabs 137B, a standard surgical instrument such as forceps can be usedfor insertion or removal of shim 36B from bearing component 32B and basecomponent 34B.

Referring to FIG. 9, base component 34B includes apertures 118B. Asillustrated in FIG. 9, two apertures 118B are located near lateralportion 92B and two apertures 118B are located near medial portion 94B.Apertures 118B could receive pegs (not shown) extending from base platesuperior surface 150B to allow base plate 38B to snap fit together withbase component 34B. Base plate 38B includes boss 174B having bossanterior side 175B, boss medial side 176B, boss posterior side 177B,boss lateral side 178B, and boss winged portions 179B.

FIGS. 10A-10C illustrate an exemplary third embodiment. Exemplary thirdembodiment provisional tibial prosthesis system 30C includes tibialbearing component 32C, base component 34C, and pin shim, component 36Chaving lateral pin 121C, medial pin 123C, and handle 125C. Tibialbearing component inferior surface 42C includes eight posts 73Cextending in a distal direction therefrom. For example, four posts 73Care located beneath medial articular surface 58C and four posts 73Cextend beneath lateral articular surface 56C. Referring to FIG. 10A,base component 34C includes eight apertures 113C extending through basecomponent 34C from inferior surface 82C to superior surface 84C. Forexample, four apertures 113C are located in medial portion 94C and fourapertures 113C are located in lateral portion 92C. Each aperture 113Creceives a single post 73C of tibial bearing component 32C therein tosecure tibial bearing component 32C to base component 34C. In theexemplary embodiment, corresponding posts 73C and apertures 113C locktibial bearing component 32C to base component 34C in medial/lateraldirection 22 and anterior/posterior direction 20. In such an embodiment,tibial bearing component 32C is moveable relative to base component 34Cin proximal/distal direction 24. However, when provisional tibialprosthesis system 30C is positioned in a knee joint, the knee joint willexert forces in proximal/distal direction 24 to keep tibial bearingcomponent 32C from pulling off base component 34C.

Referring to FIG. 10B, tibial bearing component inferior surface 42Cincludes curved lateral groove 75C and curved medial groove 77C therein,and base component superior surface 84C includes curved lateral groove115C and curved medial groove 117C therein. Lateral groove 75C andlateral, groove 115C correspond to form first mating hole portion 200Cand medial groove 77C and medial groove 117C correspond to form, secondmating hole portion 202C. Referring to FIG. 10A, mating hole portion200C receives pin 121C therein and mating hole portion 202C receives pin123C therein.

Referring to FIGS. 10A-10C, the use of pin shim 36C to change thethickness of provisional tibial, prosthesis system 30C, i.e., thedistance between tibial bearing component 32C and base component 34C,will now be described. As shown in FIG. 10A, pins 121C, 123C areslidably received between base component 34C and tibial bearingcomponent 32C, within respective mating hole portions 200C, 202C, inanterior/posterior direction 20. In an exemplary embodiment, mating holeportions 200C, 202C each have a variable mating hole diameter dh₁, dh₂.In such an embodiment, referring to FIG. 10A, the diameters of matinghole portions 200C, 202C decrease from, anterior side 48C to posteriorside 50C. For example, mating hole diameter dh₂ is greater than matinghole diameter dh₁. In this embodiment, the diameter of pins 121C, 123Care equal, i.e., pin diameter dp₁ is equal to pin diameter dp₂.Accordingly, because mating hole diameters dh₁, db₂ decrease towardsposterior side 50C, the further pin shim 36C is slid within mating holeportions 200C, 202C, the distance between tibial bearing component 32Cand base component 34C is increased.

In another exemplary embodiment, referring to FIG. 10A, the diameter ofpins 121C, 123C vary and mating hole diameters dh₁, dh₂ of mating holeportions 200C, 202C remain the same. For example, in such an embodiment,pin diameter dp₂ is greater than pin diameter dp₁ for both pins 121C and123C. Further, mating hole diameter dh₁ and dh₂ are equal throughoutmating hole portions 200C, 202C. In such an embodiment, because the pindiameters of pins 121C, 123C increase in a direction towards handle125C, the further pin shim 36C is slid within mating hole portions 200C,202C, the distance between tibial bearing component 32C and basecomponent 34C is increased.

In another exemplary embodiment, both pin diameters dp₁, dp₂ of pins121C, 123C and mating hole diameters dh₁, dh₂ of mating hole portions200C, 202C vary. For example, in such an embodiment, pin diameter dp₂ isgreater than pin diameter dp₁ for both pins 121C and 123C and matinghole diameter dh₂ is greater than mating hole diameter dh₁ for bothmating hole portions 200C, 202C. Such an embodiment allows for thegreatest thickness adjustment because not only does, the mating holediameters decrease towards posterior side 50C, the pin diametersincrease towards handle 125C. As in the previous two exemplaryembodiments, the further pin shim 36C is slid within mating holeportions 200C, 202C, the distance between tibial bearing component 32Cand base component 34G is increased.

In an exemplary embodiment, a set of different sized pin shims 36C canbe provided to allow for varying levels of adjustment of provisionaltibial prosthesis system 30C, i.e., increasing the distance betweentibial bearing component 32C and base component 34C by the diameters ofpins 121C, 123C. It is envisioned that the set; of different sized pinshims 36C could include any desired number of different sized pin shims36C having any number of different pin diameters.

FIGS. 11A and 11B illustrate an exemplary fourth embodiment. Exemplaryfourth embodiment provisional tibial prosthesis system 30D includestibial bearing component 32D, base component 34D, and sliding wedge 36D.Base component superior surface 84D includes base component medialalignment bump 114D and base component lateral alignment bump 116D.Tibial bearing component 32D is positioned on base component 34D suchthat bearing inferior surface 42D is adjacent to base component superiorsurface 84D as illustrated in FIG. 11B.

Sliding wedge 36D is generally U-shaped and includes tab 137D, lateralalignment bump 139D, medial alignment bump 141D, lateral wing 143D,anterior wedge portion 144D, and medial wing 145D. As illustrated inFIG. 11A, lateral wing 143D and medial wing 145D each include lead-inedge 140D, which function similarly to lead-in walls 146A as discussedabove. Anterior wedge portion 144D includes lateral wing 143D and medialwing 145D extending at opposing sides of anterior wedge portion 144D.Further, tab 137D extends from anterior wedge portion 144D. In anexemplary embodiment, indicia of a particular sized thickness of slidingwedge 36D can be included on tab 137D.

Sliding wedge 36D can be provided in a variety of different thicknessesto provide for varying levels of adjustment of provisional tibialprosthesis system 30D, i.e., increasing the distance between tibialbearing component 32D and base component 34D. For example, if fourdifferent sizes were to be used in the set of sliding wedges 36D, theheight of sliding wedges 36D could, be 1 mm, 2 mm, 3 mm, and 4 mm. It isenvisioned that the set of different sized sliding wedges 36D couldinclude any desired number of different sized wedges 36D having anynumber of different wedge heights.

Referring to FIGS. 11A and 11B, the use of sliding wedge 36D to changethe thickness of provisional tibial prosthesis system 30D, i.e., thedistance between tibial bearing component 32D and base component 34D,will now be described. In use, sliding wedge lateral alignment bump 139Dand sliding wedge medial alignment bump 141D are respectively alignedwith base component lateral alignment bump 116D and base componentmedial alignment bump 114D to properly orientate sliding wedge 36Dbetween tibial bearing component 32D and base component 34D. Onceproperly aligned, lead-in edges HOD of sliding wedge 36D are placedbetween tibial bearing component 32D and base component 34D to effectseparation of bearing component 32D from, base component 34D and wedge36D is slidably inserted between base component 34D and tibial bearingcomponent 32D in anterior/posterior direction 20. Alignment bumps 139B,141D of sliding wedge 36D include a protrusion portion on a proximalside and a recessed portion on a distal side.

The shims of the present disclosure can be made of a surgical gradematerial such as stainless steel, various alloys such, as acobalt-chromium alloy, and various ceramics such as silicon nitride. Theshims can also be made of various plastics including polyethylene andpolyphenylsulfone. In certain embodiments, the shims of the presentdisclosure will be disposable after a single use.

FIGS. 12A-12C illustrate an exemplary fifth embodiment. Exemplary fifthembodiment provisional tibial prosthesis system 30E includes tibialbearing component 32E, upper base component 220E, lower base component250E, and tapered screws 280E. Upper base component 220E generallyincludes upper base component inferior surface 222E, opposing upper basecomponent superior surface 224E, upper base component peripheral wall226E extending from inferior surface 222E to superior surface 224E,anterior side 228E, posterior side 230E, lateral side 232E, and medialside 234E. Tibial bearing component inferior surface 42E includescentral notch 61E extending from anterior side 48E towards posteriorside 50E and having mil 63E extending distally from inferior surface42E. In the illustrated embodiment, two protuberances 65E extend fromside wall 67E into central notch 61E at a posterior end of central notch61E.

Upper base component 220E further includes protruding member 236Eextending proximally from superior surface 224E. Protruding member 236Eincluding slot 238E spanning a proximal most portion of protrudingmember 236E from anterior side 228E to posterior side 230E. Further,protruding member 236E includes side grooves 240E. Tibial bearingcomponent 32E is positionable on upper base component 220B bypositioning rail 63E of tibial bearing component 32E within slot 238E ofupper base component 220E. This arrangement will also causeprotuberances 65E to lock into respective side grooves 240E. In such anembodiment, when tibial bearing-component 32E is positioned atop upperbase component 220E, tibial bearing component 32E is locked to upperbase component 220E in medial/lateral direction 22 and proximal/distaldirection 24. Upper base component 220E includes posts 242E extendingdistally from inferior surface 222E.

Referring to FIG. 12A, lower base component 250E generally includeslower base component inferior surface 252E, opposing lower basecomponent superior surface 254E, lower base component peripheral wall256E extending from inferior surface 252E to superior surface 254E,anterior side 258E, posterior side 260E, lateral side 262E, and medialside 264E. Lower base component 250E includes eight apertures 266Espanning from superior surface 254E to inferior surface 252E. Referringto FIG. 12A, upper base component 220E and lower base component 250E arepositioned together by inserting posts 242E of upper base component 220Ein respective apertures 266E of lower base component 250E.

Inferior surface 222E of upper base component 220E also includes curvedlateral groove 244E and curved medial groove 246E, both grooves 244E and246E being threaded. Further, superior surface 254E of lower basecomponent 250E includes curved lateral groove 268E and curved medialgroove 270E, both grooves 268E and 270E being threaded. When upper basecomponent 220E is positioned atop lower base component 250E, curvedlateral groove 244E of upper base component 220E and curved lateralgroove 268E of lower base component 250E form a first tapered, hole 290E(shown in FIG. 12B), and curved medial groove 246E of upper basecomponent 220E and curved medial groove 270E of lower base component250E form a second tapered hole 290E (shown in FIG. 12B).

Referring to FIGS. 12A-12C, the use of tapered screws 280E to adjust thethickness of provisional tibial prosthesis system 30E, i.e., thedistance between upper base component 220E and lower base component250E, will now be described. Tapered screws 280E generally includeexternal threaded portions 282E and internal female hexagon socket 284E.Tapered screws 280E are threadably inserted into respective taperedholes 290E at anterior side 48E. Tapered screw 280E includes taperedscrew diameter dts₁ at posterior end 286E and tapered screw diameterdts₂ at anterior end 288E, tapered screw diameter dts₂ being greaterthan tapered screw diameter dts₁. Further, referring to FIG. 12C, eachtapered hole 290E has tapered hole diameter dth₁ at posterior side 50Eand tapered hole diameter dth₂ at anterior side 48E, tapered holediameter dth₂ being greater than tapered hole diameter dth₁.Accordingly, as tapered screws 280E are screwed in an anterior toposterior direction, the distance between upper base component 220B andlower base component 250E is increased.

FIGS. 13A and 13B illustrate an exemplary sixth embodiment. Exemplarysixth embodiment provisional tibial prosthesis system 30F includestibial bearing component 32F, base component 34F, wedge 36F, movingmedial member 300F, moving lateral member 302F, medial base rail 308F,and lateral base rail 310F.

Base component superior surface 84F includes medial base rail 308F andlateral base rail 310F. Medial member 300F includes medial member bottomslot 304F and lateral member 302F includes lateral member bottom slot306F which respectively correspond to medial base rail 308F and lateralbase rail 310F. Slots 304F, 306F are respectively positioned atop rails308F, 310F to secure medial member 300F and lateral member 302F to basecomponent 34F. In an exemplary embodiment, slots 304F, 306F and rails308F, 310F each have a corresponding dovetail shape and cooperatetogether to act as a physical barrier to prevent lift-off of medial,member 300F and lateral member 302F from base component 34F whileallowing medial member 300F and lateral member 302F to move inmedial/lateral direction 22 over rails 308F, 310F.

Wedge component 36F generally includes wedge head portion 37F, wedgehandle 39F, wedge medial slot 41F, and wedge lateral slot 43F. Wedgecomponent 36F is attachable to medial member 300F and lateral member302F by aligning wedge medial slot 41F and wedge lateral slot 43Frespectively over medial member rail 312F and lateral member rail 314Fwhich allows wedge component 36F to slide in an anterior/posteriordirection relative to moving members 300F, 302F. As wedge component 36Fis slid in an anterior to posterior direction, wedge head portion 37Fpushes medial member 300F and lateral member 302F outward inmedial/lateral direction 22 over rails 308F, 310F. In such anembodiment, the inclined surfaces (shown in FIG. 13B) of moving medialmember 300F and moving lateral member 302F interface with inferiorsurface 42F of tibial bearing component 32F causing tibial bearingcomponent 32F to move in a proximal direction away from base component34F.

FIG. 14 illustrates an exemplary seventh embodiment. Exemplary seventhembodiment provisional tibial prosthesis system 30G includes tibialbearing component 32G, base component 34G, and gear system 36G. Basecomponent, superior surface 84G includes anterior post 95G, lateralposterior post 97G, and medial posterior post 990, posts 95G, 97G, 99Geach extending proximally from superior surface 84G.

Gear system 36G generally includes anterior gear 121G, lateral posteriorgear 123G, and medial posterior gear 124G. Posterior gears 123G, 124Ginclude annular incline surfaces 125G located on top of gears 123G,124G. Further, front anterior gear 121G includes front anterior gearteeth 127G, and posterior gears 123G, 124G each include posterior gearteeth 129G. Referring to FIG. 14, front anterior gear 121G is attachedto base component 34G by sliding aperture 131G of front anterior gear121G over anterior post 95G of base component 340. Similarly, lateralposterior gear 123G is attached to base component 34G by slidingaperture 131G of lateral posterior gear 123G over lateral post 97G ofbase component 34G and medial posterior gear 124G is attached to basecomponent 34G by sliding aperture BIG of medial posterior gear 124G overmedial posterior post 99G of base component 34G.

Referring to FIG. 14, the use of gear system 36G to adjust the distanceof tibial bearing component 32G from base component 34G will now bedescribed. The portion of front anterior gear 121G exposed from tibialbearing component 32G and base component 34G at anterior side 88G can beturned by a surgeon's ringer or a surgical instrument to turn frontanterior gear 121G which causes posterior gears 123G, 124G to rotate.Front anterior gear 121G is mechanically connected to posterior gears123G, 124G by engagement of front anterior gear teeth 127G with rearposterior gear teeth 129G of lateral posterior gear 123G and medialposterior gear 124G. Rotation of posterior gears 123G, 124G causesannular incline surface 125G of posterior gears 123G, 124G to rotate sothe thickest part of annular incline surface 125G starts to contact anInferior surface of tibial bearing component 32G which causes tibialbearing component 32G to move in a proximal direction away from basecomponent 34G.

FIG. 15 illustrates an exemplary eighth embodiment. Exemplary eighthembodiment provisional tibial prosthesis system 30H includes tibialbearing component 32H base component 34H, pry bar 36H, lateral wing 45H,and medial wing 47H. Base component superior surface 84H includes aplurality of steps 85H that are respectively located a distance closerto an inferior surface of tibial bearing component 32H as steps 85Hextend inwardly from medial side 54H and lateral side 52H.

Referring to FIG. 15, the use of exemplary eighth embodiment provisionaltibial prosthesis system 30H will now be described. As shown in FIG. 15,pry bar 36H is movably connected to tibial bearing component 32H andbase component 34H via support members 41H and pins 43H. In such anembodiment, exerting a force on tab 37H of pry bar 36H pushes up liftingmember 39H of pry bar 36B to move tibial bearing component 32H away frombase component 34H. As the distance between tibial bearing component 32Hand base component 34H increases via pry bar 36H, spring-loaded lateralwing 45H and medial wing 47H rotate inward towards pry bar 36H to thenext step 85H. Lateral wing 45H and medial wing 47H maintain thedistance between tibial bearing component 32H and base component 34Hcreated by pry bar 36H. If a greater thickness is desired, tab 37H ofpry bar 36H can again be depressed causing lifting member 39H of pry bar36H to further move tibial bearing component 32H away from basecomponent 34H causing lateral wing 45H and medial wing 47H to againrotate inwards to the next level step 85H. In this manner, lateral wing45H and medial wing 47H again maintain the distance between tibial,bearing component 32H and base component 34H created by pry bar 36H. Toreset the distance between tibial bearing component 32H and basecomponent 34H to an initial position, lateral exposed end 49H of lateralwing 45H and medial exposed end 51H of medial wing 47H can be pushed inan outward direction away from, pry bar 36H to push lateral wing 45H andmedial wing 47H back to the initial position causing tibial bearingcomponent 32H to collapse back to an initial position relative to basecomponent 34H.

FIGS. 16A-16C illustrate an exemplary ninth embodiment. Exemplary ninthembodiment provisional tibial, prosthesis system 30I includes tibialbearing component 32I, base component 34I, threaded cylinder 36I, andlocking cylinders 37I. Referring to FIGS. 16A-16C, the use of exemplaryninth embodiment provisional tibial prosthesis system 30I will now bedescribed. Threaded cylinder 36I is positioned between tibial bearingcomponent 32I and base component 34I by threadably attaching threadedcylinder 36I to threaded anterior post 85I extending from base componentsuperior surface 84I. Threaded cylinder 36I is attached to tibialbearing component 32I via locking cylinders 37I. Referring to FIG. 16C,locking cylinders 37I are securely positioned within threaded cylinderannular groove 39I to threaded cylinder 36I, and are also securelypositioned within tibial bearing component receiving apertures 63I totibial bearing component 32I. Locking cylinders 37I prohibit relativeaxial movement between cylinder 36I and bearing component 32I whileallowing relative rotational movement between cylinder 36I and bearingcomponent 32I. Posts 87I, 89I prevent bearing component 32I fromrotating relative to base component 34I.

In use, a tool having a hexagonal cross-section can be inserted ininternal female hexagon socket 41I of threaded cylinder 36I to rotatethreaded cylinder 36I on threaded anterior post 85I of base component34I. As threaded cylinder 36I rotates and moves away from base component34I, tibial bearing component 32I which is connected to threadedcylinder 36I via locking cylinders 37I travels with threaded cylinder36I in a proximal direction away from base component 34I.

FIGS. 17A-17C illustrate an exemplary tenth embodiment. Exemplary tenthembodiment provisional tibial prosthesis system 30J includes tibialbearing component 32J, base component 34 j, and component wedge assembly36J. Component wedge assembly 36J includes wedge head portion 37J havingtab 39J exposed from tibial bearing component 32J, lateral wedge 41J,and medial wedge 43J. Wedge head portion 37J, lateral wedge 41J, andmedial wedge 43J form an integral wedge piece that can move inanterior/posterior direction 20 relative to tibial bearing component 32Jand base component 34J within tibial bearing component cavity 65J.Referring to FIGS. 17A-17C, the use of exemplary tenth embodimentprovisional tibial prosthesis system 30J will now be described. As shownin FIGS. 17A and 17C, as tab 39J is pushed in an anterior to posteriordirection, teeth 45J grab a portion of tibial bearing component 32J toprevent wedge assembly 36J from anterior movement when no force isexerted on tab 39J. As tab 39J of wedge head portion 37J is moved in ananterior to posterior direction, attached lateral wedge 41J and medialwedge 43J also move within tibial bearing component cavity 65J in theanterior to posterior direction. As wedge head portion 37J is pushedanterior to posterior, the inclined surfaces 47J of lateral wedge 41Jand medial wedge 43J move tibial bearing component 32J away from basecomponent 34J. To reduce the distance between tibial bearing component32J and base component 34J, a force is exerted on tab 39J to disengageteeth 45J from bearing component 32J and then tab 39J is pulled backtoward anterior side 48J to pull component wedge assembly 36J from aposterior to anterior direction, thus decreasing the distance betweentibial bearing component 32J and base component 34J.

FIGS. 18A-18B illustrate an exemplary eleventh embodiment. Exemplaryeleventh embodiment provisional tibial, prosthesis system 30K includestibial bearing component 32K, base component 34K, rotating knob 36K,medial tapered pin 37K, and lateral tapered pin 39K. Rotating knob 36Kis movably connected with medial tapered pin 37K and lateral tapered pin39K via connecting rod 41K. Further, rotating knob 36K, medial taperedpin 37K, lateral tapered pin 39K, and connecting rod 41K are eachpositioned between tibial bearing component 32K and base component 34 k,and are rotatable relative to tibial bearing component 32K and basecomponent 34K. Inferior surface 42K of tibial bearing component 32Kincludes curved medial groove 65K and curved lateral groove 67K. Basecomponent superior surface 84K includes corresponding curved medialgroove 85K and curved lateral groove 87K which respectively correspondto curved medial groove 65K and curved lateral groove 67K of tibialbearing component 32K to create receiving hole 290K which receivesmedial tapered pin 37K, lateral tapered pin 39K, and connecting rod 41K.

As shown in FIG. 18A, portion 43K of rotating knob 36K is exposed fromtibial bearing component 32K to allow knob 36K to be rotated in aclockwise direction or a counterclockwise direction. Referring to FIGS.18A and 18B, the use of exemplary eleventh embodiment 30K will now bedescribed. As knob 36K is rotated in a first direction, both medialtapered pin 37K and lateral tapered pin 39K are rotated in receivinghole 290K in a direction towards knob 36 k. In such an embodiment,medial tapered pin 37K and lateral tapered pin 39K are tapered such thatthe end of both medial tapered pin 37K and lateral tapered pin 39Kfarthest from knob 36K has a diameter greater than the end of medialtapered pin 37K and lateral tapered pin 39K which is closest to knob36K. For this reason, as knob 36K rotates medial tapered pin 37K andlateral tapered pin 39K toward knob 36K, the end of medial tapered pin37K and lateral tapered pin 39K which has the greatest diameter is movedinward towards knob 36K to move tibial bearing component 32K away frombase component 34K. In the illustrated embodiment, rotation of knob 36Kin a second direction, opposite the first direction, will cause medialtapered pin 37K and lateral tapered pin 39K to rotate in a direction away from knob 36K to decrease the distance between, tibial bearingcomponent 32K and base component 34K.

While this disclosure has been described as having exemplary designs,the present disclosure can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the disclosure using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this disclosure pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A tibial prosthesis system for implantation on aresected surface of a proximal tibia, the tibial prosthesis systemcomprising: a bearing component having a superior articulating surfaceand an inferior surface; a base component having a superior surface andan inferior surface; and a shim component configured to be removablyreceived between the inferior surface of the bearing component and thesuperior surface of the base component by inserting the shim componentin a first direction, wherein the shim component is restrained frommovement in a second direction substantially perpendicular to the firstdirection once the shim component engages with at least one of thebearing component and the base component.
 2. The tibial prosthesissystem of claim 1, wherein the first direction is an anterior/posteriordirection and the second direction is a medial/lateral direction.
 3. Thetibial prosthesis system of claim 1, wherein the shim component includesone or more tapering walls on an end of the shim component to guideinsertion of the shim component in the first direction.
 4. The tibialprosthesis system of claim 3, wherein the one or more tapering walls areon a posterior end of the shim component to guide insertion of the shimcomponent in the first direction and to separate the bearing componentfrom the base component by a proximal/distal distance equal to aproximal/distal height of the shim component, and the first direction isan anterior/posterior direction.
 5. The tibial prosthesis system ofclaim 1, further comprising: a shim handling instrument configured toreleasably secure the shim component to aid in inserting and removingthe shim component from between the bearing component and the basecomponent.
 6. The tibial prosthesis system of claim 5, wherein the shimhandling instrument includes one or more features configured to engagewith features formed on an end of the shim component.
 7. The tibialprosthesis system of claim 6, wherein the shim handling instrumentincludes a tooth configured to releasably lock the shim handlinginstrument to the shim component, and a release button configured todisengage the tooth from the shim component.
 8. The tibial prosthesissystem of claim 1, further comprising: a tibial baseplate having a bonecontacting surface and an opposing baseplate superior surface, whereinthe base component is secured to the tibial baseplate.
 9. The tibialprosthesis system of claim 1, wherein the tibial prosthesis systemfurther comprises at least one of a first lock and a second lock forlocking the bearing component to the base component in a proximal/distaldirection, whereby significant relative movement between the bearingcomponent and the base component in the proximal/distal direction isprevented.
 10. The tibial prosthesis system of claim 9, wherein the basecomponent comprises a protrusion extending from the superior surface ofthe base component and an indentation formed between the protrusion andthe superior surface, the first lock including rails on a superiorsurface of the shim configured to engage with slots on the inferiorsurface of the bearing component, and the second lock comprising a notchformed on a posterior side of the shim configured to engage with theindentation on the base component.
 11. The tibial prosthesis system ofclaim 9, wherein the tibial prosthesis system further comprises a thirdlock, wherein when the bearing component is attached to the basecomponent, the third lock locks the tibial bearing component to the basecomponent in a medial/lateral direction and an anterior/posteriordirection, whereby significant relative movement between the bearingcomponent and the base component in the medial/lateral direction and theanterior/posterior direction is prevented.
 12. The tibial prosthesissystem of claim 11, wherein the third lock comprises a protrusionextending from the superior surface of the base component and a cavityformed in the bearing component.
 13. The tibial prosthesis system ofclaim 12, wherein the third lock further comprises one or more nubcavities in the bearing component configured to engage with one or morenubs extending from the protrusion of the base component.
 14. A tibialprosthesis system, comprising: a bearing component having a superiorarticulating surface and an inferior surface; a base component having asuperior surface and an inferior surface; and a plurality of shimcomponents including shim components having different heights relativeto each other, each shim component configured to be removably receivedbetween the inferior surface of the bearing component and the superiorsurface of the base component by inserting the shim component in a firstdirection, wherein each of the shim components is restrained frommovement in a second direction substantially perpendicular to the firstdirection once the shim component engages with at least one of thebearing component and the base component.
 15. The tibial prosthesissystem of claim 14, wherein the plurality of shim components includes atleast a first shim component having a first shim height in aproximal/distal direction and a second shim component having a secondshim height in a proximal/distal direction different than the first shimheight.
 16. The tibial prosthesis system of claim 15, wherein the firstshim component and the second shim component are insertable between thebearing component and the base component such that the bearing componentand the base component are separated by a distance equal to a sum of thefirst shim height and the second shim height.
 17. The tibial prosthesissystem of claim 15, wherein a selection of the first shim component orthe second shim component for use with the bearing component and thebase component includes a determination of which of the first shimcomponent or the second shim component creates a proper spacing betweenthe bearing component and the base component when the bearing componentand the base component are positioned on a resected surface of aproximal tibia.
 18. A method of performing a surgical procedure on aportion of a knee joint, the method comprising: implanting a tibialprosthesis on a resected tibia, the tibial prosthesis including abearing component and a base component; inserting a first shim componentin a first direction between the bearing component and the basecomponent, the first shim component being restrained from movement in asecond direction substantially perpendicular to the first direction oncethe first shim component engages with at least one of the bearingcomponent and the base component, whereby the bearing component and thebase component are spaced apart by a proximal/distal distance equal to afirst shim height of the first shim component; performing range ofmotion testing to verify proper sizing of the tibial prosthesis; andwhen the testing indicates that the tibial prosthesis is not properlysized, inserting a second shim component in the first direction betweenthe bearing component and the base component, the second shim componentbeing restrained from movement in the second direction.
 19. The methodof claim 18, further comprising: prior to inserting the second shimcomponent between the bearing component and the base component, removingthe first shim component from between the base component and the bearingcomponent, wherein the second shim component has a second shim heightdifferent than the first shim height, and the bearing component and thebase component are spaced apart by a proximal/distal distance equal tothe second shim height, after inserting the second shim component. 20.The method of claim 18, wherein the second shim component has a secondshim height, and the bearing component and the base component are spacedapart by a proximal/distal distance equal to a sum of the first shimheight and the second shim height.
 21. The method of claim 18, whereinthe first direction is an anterior/posterior direction and the seconddirection is a medial/lateral direction.
 22. The method of claim 18,wherein the tibial prosthesis includes a baseplate having a bonecontacting surface and an opposing superior surface, and the basecomponent is secured to the baseplate.
 23. The method of claim 18,wherein inserting the first shim component between the bearing componentand the base component prevents significant relative movement betweenthe bearing component and the base component in the proximal/distaldirection.